A solid oxide fuel cell (hereinafter, referred to as SOFC) is known as a highly efficient fuel cell having a wide range of applications. Such an SOFC has a high operating temperature in order to increase ionic conductivity. Thus, air that has been discharged from a compressor of a gas turbine is usable as the air to be supplied to an air electrode (as an oxidant). The SOFC also enables unused high-temperature fuel to be used as fuel for a combustor of the gas turbine.
Thus, for example, as described in Patent Literature 1 listed below, various combinations of an SOFC, a gas turbine, and a steam turbine have been proposed as a power generation system that achieves highly efficient power generation. The combined system described in Patent Literature 1 is provided with an SOFC, a gas turbine combustor that combusts exhaust fuel gas and exhaust air discharged from the SOFC, and a gas turbine having a compressor that compresses air and supplies it to the SOFC.
In addition, Patent Literature 2 describes a technique in which exhaust air discharged from the SOFC exchanges heat with air to be supplied to the SOFC, followed by heat exchange with plumbing of a heat recovery steam generator, so that the heat of the exhaust air is used for power generation of the heat recovery steam generator.